Where do the mysterious witch circles come from in the African desert

(ORDO NEWS) — In the Namib Desert there are huge areas covered with a geometric pattern of vegetation: grasses in these places grow in rings. What forms the amazing desert landscape?

About a hundred kilometers off the southwest coast of Africa, in the Namib Desert, an alien landscape awaits any traveler: millions of strange circles on which nothing grows.

These “clearings” devoid of any vegetation of regular rounded shape sometimes have a diameter of several meters.

As if some witch had spilled drops of her potion here, and where they fell, nothing alive grows. Such “witch circles” are commonly found in the pastures of the Namib, which is considered the oldest desert in the world.

Namib crosses the borders of three countries, and a significant part of the desert is located on the territory of Namibia. For an observer who looks around the pastures of the Namib, a “magic” pattern opens up, sometimes stretching for many kilometers around.

Where do the mysterious witch circles come from in the African desert 2
“Fairytale” circles of the Namib

Researchers have been puzzling over the origins of Namibian witch circles for nearly half a century.

All scientific research during this time has been reduced to two main theories: either termites are to blame for the appearance of “bald spots” on the soil, or the herbs growing there somehow self-organize into such circles.

The lack of clarity in such matters is a real challenge for scientists. What is happening in the Namib territory in reality? This time, researchers from the University of Göttingen in Germany decided to make their verdict.

They benefited from two exceptionally good rainy seasons in the desert.

Ecologists monitored periodic rains in several regions of the Namib and studied grasses, their roots and shoots, including looking for possible root damage caused by termites.

Soil moisture sensors that the researchers installed in and around the mysterious circles recorded soil moisture content at 30-minute intervals from the 2020 dry season to the 2022 rainy season.

Then the authors of the work scrupulously studied the circumstances of the death of plants in witch circles immediately after the rain, which initially caused a surge in the growth of grasses.

The authors of the new work found that the grasses in the circles died immediately after the rain, but this was not due to termites, which are often blamed for the death of plants.

The data show that about 10 days after the rain, the grasses inside the circles were already starting to die back. At the same time, grass did not germinate at all on the larger inner area of ​​the circles.

20 days after the rain, all the meager grass cover inside the circles was completely dry and turned yellow. This contrasted strongly with how green and full of life the grasses that bordered this “bald spot” were.

When the researchers examined the roots of the dried grasses inside the circles and compared them to the roots of the green grasses outside, they found that the roots of the plants growing inside the circles were as long, and sometimes longer, than the roots of the plants outside.

This means that the herbs growing in the center of the circle tried their best to put down deep roots in search of water, but could not get enough of it.

The scientists also analyzed the obtained data on fluctuations in soil moisture. They noticed that after the initial rains, when the grasses were still breaking through, the soil moisture levels inside and outside the circles decreased very slowly.

However, when the surrounding grasses were well established after the rain, the amount of soil moisture began to decline rapidly in all parts of the circle. This is curious, because inside the circles there was almost no grass that could absorb water.

At the same time, the researchers did not find any evidence that termites destroyed the plant roots. Damage to the roots associated with the vital activity of these insects appeared only 50-60 days after the beginning of the drying of the soil.

The authors of the study believe that it is grasses that form the patterned landscapes of evenly spaced witch circles. They act as ecosystem engineers who seek to make the most of available (and very limited) water resources.

Scientists know of other types of plants that form similar self-organizing structures. They mostly grow in harsh arid conditions. These plants have no other chance to survive than to grow in exactly these geometric shapes.

This self-organization of plants protects them from the negative effects of increasingly long and intense periods of aridity.

Climate change in the coming decades will lead to more frequent and severe droughts, especially in Africa. At the same time, the situation in some countries of the Black Continent is already catastrophic. But nature can suggest ways for humanity to adapt to such changes.

Therefore, researchers seek to understand the structure of such “magic” ecosystems.

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